It is often desirable to remove hydrogen from a mixture of hydrogen and one or more organic compounds, for example in a process for the dehydrogenation of organic compounds.
In a process for the dehydrogenation of organic compounds, the position of thermodynamic equilibrium between dehydrogenatable organic compounds and dehydrogenated organic compounds depends upon the amount of hydrogen present. This may be appreciated from the equation give below: EQU dehydrogenatable organic compounds .revreaction.dehydrogenated compounds+H.sub.2.
Accordingly, in a dehydrogenation process, it may be desirable to remove hydrogen from a mixture of hydrogen and dehydrogenatable and dehydrogenated organic compounds in order to shift the position of thermodynamic equilibrium in favor of dehydrogenated compounds.
Many different techniques are know for the removal of a substance from a mixture of that substance with others. Examples of such techniques include crystallization, distillation, liquefaction, solvent extraction, absorption, membrane separation and chemical reaction. However, it is in practice difficult to remove hydrogen from a mixture of hydrogen and one or more organic compounds, especially a mixture of hydrogen and dehydrogenatable and dehydrogenated organic compounds.
Numerous processes have been disclosed which involved the removal of hydrogen from a mixture of hydrogen and one or more organic compounds. For example, U.S. Pat. No. 4,788,371 discloses a process for the dehydrogenation of hydrocarbons in which hydrogen obtained by the dehydrogenation of the hydrocarbons is chemically reacted with oxygen gas in the presence of a particular catalyst. The specification refers to several other U.S. Pat. specifications which also disclose processes in which hydrogen is chemically reacted with oxygen gas. A disadvantage of all of these processes is that some of the oxygen gas reacts chemically with organic compounds instead of hydrogen, thus converting them into undesired products.
European Pat. No. A1-0219271 and No. A1-0219272 also disclose processes for the dehydrogenation of hydrocarbons in which hydrogen obtained by the dehydrogenation of the hydrocarbons is removed. In these processes, the dehydrogenation takes place in the presence of a zeolite catalyst, and the hydrogen is removed by chemical reaction with an acidic oxide gas such as sulfur dioxide or nitrous oxide. The processes do not share the disadvantage of the processes which use oxygen gas, because sulfur dioxide and nitrous oxide are not as reactive as oxygen towards the organic compounds. However, the processes appear to be poorly effective for the removal of hydrogen.
It has now been found that hydrogen can be removed very effectively and with high selectivity using certain molecular sieves containing a reducible metal cation.